Cooling arrangement for platform region of turbine rotor blade

ABSTRACT

A platform cooling arrangement in a turbine rotor blade having a platform at an interface between an airfoil and a root. The platform may include a pressure side slashface and a suction side slashface. The platform cooling arrangement may include: a cooling channel formed within the interior of the platform, the cooling channel extending from a first end toward one of the pressure side slashface and the suction side slashface. At a second end, the cooling channel may include a pocket. The pocket may include an abrupt increase in cross-sectional flow area just before the cooling channel reaches the slashface.

BACKGROUND OF THE INVENTION

The present application relates generally to combustion turbine engines, which, as used herein and unless specifically stated otherwise, includes all types of combustion turbine engines, such as those used in power generation and aircraft engines. More specifically, but not by way of limitation, the present application relates to apparatus, systems and/or methods for cooling the platform region of turbine rotor blades.

A gas turbine engine typically includes a compressor, a combustor, and a turbine. The compressor and turbine generally include rows of airfoils or blades that are axially stacked in stages. Each stage typically includes a row of circumferentially spaced stator blades, which are fixed, and a set of circumferentially spaced rotor blades, which rotate about a central axis or shaft. In operation, the rotor blades in the compressor are rotated about the shaft to compress a flow of air. The compressed air is then used within the combustor to combust a supply of fuel. The resulting flow of hot gases from the combustion process is expanded through the turbine, which causes the rotor blades to rotate the shaft to which they are attached. In this manner, energy contained in the fuel is converted into the mechanical energy of the rotating shaft, which then, for example, may be used to rotate the coils of a generator to generate electricity.

Referring to FIGS. 1 and 2, turbine rotor blades 100 generally include an airfoil portion or airfoil 102 and a root portion or root 104. The airfoil 102 may be described as having a convex suction face 105 and a concave pressure face 106. The airfoil 102 further may be described as having a leading edge 107, which is the forward edge, and a trailing edge 108, which is the aft edge. The root 104 may be described as having structure (which, as shown, typically includes a dovetail 109) for affixing the blade 100 to the rotor shaft, a platform 110 from which the airfoil 102 extends, and a shank 112, which includes the structure between the dovetail 109 and the platform 110.

As illustrated, the platform 110 may be substantially planar. More specifically, the platform 110 may have a planar topside 113, which, as shown in FIG. 1, may include an axially and circumferentially extending flat surface. As shown in FIG. 2, the platform 110 may have a planar underside 114, which may also include an axially and circumferentially extending flat surface. The topside 113 and the bottom side 114 of the platform 110 may be formed such that each is substantially parallel to the other. As depicted, it will be appreciated that the platform 110 typically has a thin radial profile, i.e., there is a relatively short radial distance between the topside 113 and the bottom side 114 of the platform 110.

In general, the platform 110 is employed on turbine rotor blades 100 to form the inner flow path boundary of the hot gas path section of the gas turbine. The platform 110 further provides structural support for the airfoil 102. In operation, the rotational velocity of the turbine induces mechanical loading that creates highly stressed regions along the platform 110 that, when coupled with high temperatures, ultimately cause the formation of operational defects, such as oxidation, creep, low-cycle fatigue cracking, and others. These defects, of course, negatively impact the useful life of the rotor blade 100. It will be appreciated that these harsh operating conditions, i.e., exposure to extreme temperatures of the hot gas path and mechanical loading associated with the rotating blades, create considerable challenges in designing durable, long-lasting rotor blade platforms 110 that both perform well and are cost-effective to manufacture.

One common solution to make the platform region 110 more durable is to cool it with a flow of compressed air or other coolant during operation, and a variety of these type of platform designs are known. However, as one of ordinary skill in the art will appreciate, the platform region 110 presents certain design challenges that make it difficult to cool in this manner. In significant part, this is due to the awkward geometry of this region, in that, as described, the platform 110 is a periphery component that resides away from the central core of the rotor blade and typically is designed to have a structurally sound, but thin radial thickness.

To circulate coolant, rotor blades 100 typically include one or more hollow cooling passages 116 (see FIGS. 3, 4, 5, and 9) that, at minimum, extend radially through the core of the blade 100, including through the root 104 and the airfoil 102. As described in more detail below, to increase the exchange of heat, such cooling passages 116 may be formed having a serpentine path that winds through the central regions of the blade 100, though other configurations are possible. In operation, a coolant may enter the central cooling passages via one or more inlets 117 formed in the inboard portion of the root 104. The coolant may circulate through the blade 100 and exit through outlets (not shown) formed on the airfoil and/or via one or more outlets (not shown) formed in the root 104. The coolant may be pressurized, and, for example, may include pressurized air, pressurized air mixed with water, steam, and the like. In many cases, the coolant is compressed air that is diverted from the compressor of the engine, though other sources are possible. As discussed in more detail below, these cooling passages typically include a high-pressure coolant region and a low-pressure coolant region. The high-pressure coolant region typically corresponds to an upstream portion of the cooling passage that has a higher coolant pressure, whereas the low-pressure coolant region corresponds to a downstream portion having a relatively lower coolant pressure.

In some cases, the coolant may be directed from the cooling passages 116 into a cavity 119 formed between the shanks 112 and platforms 110 of adjacent rotor blades 100. From there, the coolant may be used to cool the platform region 110 of the blade, a conventional design of which is presented in FIG. 3. This type of design typically extracts air from one of the cooling passages 116 and uses the air to pressurize the cavity 119 formed between the shanks 112/platforms 110. Once pressurized, this cavity 119 then supplies coolant to cooling channels that extend through the platform 110. After traversing the platform 110, the cooling air may exit the cavity through film cooling holes formed in the topside 113 of the platform 110.

It will be appreciated, however, that this type of conventional design has several disadvantages. First, the cooling circuit is not self-contained in one part, as the cooling circuit is only formed after two neighboring rotor blades 100 are assembled. This adds a great degree of difficulty and complexity to installation and pre-installation flow testing. A second disadvantage is that the integrity of the cavity 119 formed between adjacent rotor blades 100 is dependent on how well the perimeter of the cavity 119 is sealed. Inadequate sealing may result in inadequate platform cooling and/or wasted cooling air. A third disadvantage is the inherent risk that hot gas path gases may be ingested into the cavity 119 or the platform itself 110. This may occur if the cavity 119 is not maintained at a sufficiently high pressure during operation. If the pressure of the cavity 119 falls below the pressure within the hot gas path, hot gases will be ingested into the shank cavity 119 or the platform 110 itself, which typically damages these components as they were not designed to endure exposure to the hot gas-path conditions.

FIGS. 4 and 5 illustrate another type of conventional design for platform cooling. In this case, the cooling circuit is contained within the rotor blade 100 and does not involve the shank cavity 119, as depicted. Cooling air is extracted from one of the cooling passages 116 that extend through the core of the blade 110 and directed aft through cooling channels 120 formed within the platform 110 (i.e., “platform cooling channels 120”). As shown by the several arrows, the cooling air flows through the platform cooling channels 120 and exits through outlets in the aft edge 121 of the platform 110 or from outlets disposed along the suction side edge 122. (Note that in describing or referring to the edges or faces of the rectangular platform 110, each may be delineated based upon its location in relation to the suction face 105 and pressure face 106 of the airfoil 102 and/or the forward and aft directions of the engine once the blade 100 is installed. As such, as one of ordinary skill in the art will appreciate, the platform may include an aft edge 121, a suction side edge 122, a forward edge 124, and a pressure side edge 126, as indicated in FIGS. 3 and 4. In addition, the suction side edge 122 and the pressure side edge 126 also are commonly referred to as “slashfaces” and the narrow cavity formed therebetween once neighboring rotor blades 100 are installed may be referred to as a “slashface cavity”.)

It will be appreciated that the conventional designs of FIGS. 4 and 5 have an advantage over the design of FIG. 3 in that they are not affected by variations in assembly or installation conditions. However, conventional designs of this nature have several limitations or drawbacks. First, as illustrated, only a single circuit is provided on each side of the airfoil 102 and, thus, there is the disadvantage of having limited control of the amount of cooling air used at different locations in the platform 110. Second, conventional designs of this type have a coverage area that is generally limited. While the serpentine path of FIG. 5 is an improvement in terms of coverage over FIG. 4, there are still dead areas within the platform 110 that remain uncooled. Third, to obtain better coverage with intricately formed platform cooling channels 120, manufacturing costs increase dramatically, particularly if the cooling channels having shapes that require a casting process to form. Fourth, these conventional designs typically dump coolant into the hot gas path after usage and before the coolant is completely exhausted, which negatively affects the efficiency of the engine. Fifth, conventional designs of this nature generally have little flexibility. That is, the channels 120 are formed as an integral part of the platform 110 and provide little or no opportunity to change their function or configuration as operating conditions vary. In addition, these types of conventional designs are difficult to repair or refurbish.

Another issue relates to the difficulties around cooling the pressure side and suction side slashfaces 126, 122. Conventional designs may include ports located on the slashfaces 126, 122 for the release of coolant. The ports are configured to release an impinged, high-velocity stream of coolant. However, with these conventional techniques, the ports lack sophisticated exit geometry, which results in a steep thermal gradient around each of the port and, more generally, along the slashfaces of the platform, as well as, at the target surface of the impingement stream. Such thermal gradients increase the degradation within this region of the rotor blade. As a result, conventional platform cooling designs are lacking in one or more significant criteria. There remains a need for improved apparatus, systems, and methods that effectively and efficiently cool the platform region of turbine rotor blades, while also being cost-effective to construct, flexible in application, and durable.

BRIEF DESCRIPTION OF THE INVENTION

The present application thus describes a platform cooling arrangement in a turbine rotor blade having a platform at an interface between an airfoil and a root. The platform may include a pressure side slashface and a suction side slashface. The platform cooling arrangement may include: a cooling channel formed within the interior of the platform, the cooling channel extending from a first end toward one of the pressure side slashface and the suction side slashface. At a second end, the cooling channel may include a pocket. The pocket may include an abrupt increase in cross-sectional flow area just before the cooling channel reaches the slashface.

These and other features of the present application will become apparent upon review of the following detailed description of the preferred embodiments when taken in conjunction with the drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will be more completely understood and appreciated by careful study of the following more detailed description of exemplary embodiments of the invention taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a perspective view of an exemplary turbine rotor blade in which embodiments of the present invention may be employed;

FIG. 2 illustrates an underside view of a turbine rotor blade in which embodiments of the present invention may be used;

FIG. 3 illustrates a sectional view of neighboring turbine rotor blades having a cooling system according to conventional design;

FIG. 4 illustrates a top view of a turbine rotor blade having a platform with interior cooling channels according to conventional design;

FIG. 5 illustrates a top view of a turbine rotor blade having a platform with interior cooling channels according to an alternative conventional design;

FIG. 6 illustrates a perspective view of a turbine rotor blade having a platform cooling configuration according to an exemplary embodiment of the present invention;

FIG. 7 illustrates a top with partial cross-sectional view of a platform of a turbine rotor blade having a cooling configuration according to an exemplary embodiment of the present invention;

FIG. 8 illustrates a front view from the vantage point along 8-8 of FIG. 7;

FIG. 9 illustrates a cross-sectional view along 9-9 of FIG. 7;

FIG. 10 illustrates a side view of a platform cooling configuration according to an alternative embodiment of the present application;

FIG. 11 illustrates a side view of a platform cooling configuration according to an alternative embodiment of the present application; and

FIG. 12 illustrates a top with partial cross-sectional view of a turbine rotor blade having a platform cooling configuration according to an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As discussed above, various conventional designs of internal cooling passages 116 are somewhat effective at cooling certain regions within a rotor blade 100. However, as one of ordinary skill in the art will appreciate, the platform region proves more challenging. This is due, at least in part, to the awkward geometry of the platform—i.e., its narrow radial height and the manner in which it juts away from the core or main body of the rotor blade 100. Nevertheless, given its exposures to the extreme temperatures of hot gas path and high mechanical loading, the cooling requirements of the platform 110 are considerable. As described above, conventional platform cooling designs are ineffective because they fail to address the particular challenges of the region, are inefficient with their usage of coolant, and/or are costly to fabricate.

Several particular descriptive terms may be used to describe exemplary embodiments of the present application. The meaning for these terms shall include the following definitions. The terms “downstream” and “upstream” are terms that indicate a direction relative to the flow of working fluid through the turbine or, as the case may be, coolant through a cooling passage. Accordingly, the term “downstream” means the direction of the flow, and the term “upstream” means in the opposite direction of the flow. The term “radial” refers to movement or position perpendicular to an axis. It is often required to describe parts that are at differing radial positions with regard to this axis. In these cases, if a first component resides closer to the axis than a second component, it may be stated herein that the first component is either “inboard” or “radially inward” of the second component. If, on the other hand, the first component resides further from the axis than the second component, it may be stated herein that the first component is “outboard” or “radially outward” of the second component. The term “axial” refers to movement or position parallel to an axis. And, the term “circumferential” refers to movement or position around an axis. Unless otherwise stated, when the terms “radial”, “axial”, or “circumferential” are used, they are used in reference to the central axis of the turbine engine.

It will be appreciated that turbine blades that are cooled via the internal circulation of a coolant typically include an interior cooling passage 116 that extends radially outward from the root, through the platform region, and into the airfoil, as described above in relation to several conventional cooling designs. It will be appreciated that certain embodiments of the present invention may be used in conjunction with conventional coolant passages to enhance or enable efficient active platform cooling, and the present invention is discussed in connection with an exemplary common design: an interior cooling passage 116 having a winding or serpentine configuration. As depicted in FIGS. 5 and 7, the serpentine path is typically configured to allow a one-way flow of coolant and includes features that promote the exchange of heat between the coolant and the surrounding rotor blade 100. In operation, a pressurized coolant, which typically is compressed air bled from the compressor (though other types of coolant, such as steam, also may be used with embodiments of the present invention), is supplied to the interior cooling passage 116 through a connection formed through the root 104. The pressure drives the coolant through the interior cooling passage 116, and the coolant convects heat from the surrounding walls. It will be appreciated that the present invention may be used in rotor blades 100 having internal cooling passages of different configurations and is not limited to interior cooling passages having a serpentine form. Accordingly, as used herein, the term “interior cooling passage” or “cooling passage” is meant to include any passage or hollow channel through which coolant may be circulated in the rotor blade. As provided herein, the exemplary interior cooling passage 116 extends to at least to the approximate radial height of the platform 116. Though not shown, it will be appreciated that the present invention may also be employed using a shank fed coolant source, such as the one illustrated in FIG. 3.

Referring now to FIGS. 6 through 12, several views of exemplary embodiments of the present invention are provided. The present application describes depressive geometrical features or pockets formed along the slash faces of the platform of turbine rotor blades. These features include a set of pockets that connect to interior coolant channels formed through the platform, which may be supplied with coolant from interior channels in the root of the rotor blade or from the shank cavity that is formed between two adjacent rotor blades. It will be appreciated that, as described in detail below, the depressive geometrical features of the present application may be employed to defuse and slow the coolant just before the coolant is expelled from the platform, which may results in the beneficial reduction of thermal gradients at the slashface of rotor blades.

FIGS. 6 through 12 illustrate a turbine rotor blade 100 having a platform cooling configuration 130 according to preferred embodiments of the present invention. As shown, the rotor blade 100 includes a platform 110 residing at the interface between an airfoil 102 and a root 104. In the exemplary embodiment shown, the rotor blade 100 includes an interior cooling passage 116 that extends from the root 104 to the radial height of the platform 110, and, in this case, into the airfoil 102. At the side of the platform 110 that corresponds with a pressure face 106 of the airfoil 102, it will be appreciated that the platform 110 may have a planar topside 113 that extends from the airfoil 102 to a pressure side slashface 126. (Note that “planar,” as used herein, means approximately or substantially in the shape of a plane. For example, one of ordinary skill in the art will appreciate that platforms may be configured to have an outboard surface that is slight curved and convex, with the curvature corresponding to the circumference of the turbine at the radial location of the rotor blades. As used herein, this type of platform shape is deemed planar, as the radius of curvature is sufficiently great to give the platform a flat appearance.)

Configured within the interior of the platform 110, an exemplary embodiment of the present invention includes different types of hollow passageways that are configured to distribute coolant through regions of the platform 110. Though other configurations are possible, in a preferred embodiment, these hollow coolant passageways include one or more plenums 132; one or more connectors 134 (which connects the plenum 132 to the interior cooling passage 116); a plurality of cooling channels 136, each of which branches from one of the plenum 132 at one end and includes, at the other end, a pockets 144 positioned along the pressure side slashface 126 (or, in alternative embodiments, the suction side slashface 122). The pocket 144 may include a port 146 through which coolant flowing through the cooling channel enters the pocket 144.

In certain embodiments, a plurality of pockets 144 is dispersed along the pressure side slashface 126. As illustrated, each pocket 144, in general, is a concave depression or bowl-like feature formed in the pressure side slashface 126. Each pocket 144 includes a mouth 148 residing coplanar to the plane of the slashface 126. As shown in FIG. 8, the profile of the mouth 148 may be rectangular as shown, though other shapes are possible. From the mouth 148, the pocket 144 extends into the platform 110 a relatively short distance to an inner wall 149, which is opposite the mouth 148. The port 146 may be formed in the inner wall 149 of the pocket 144. The pocket 144 may be described as having a depth, which describes a circumferential depth of the pocket 144 or, put another way, the distance between the mouth 148 and the inner wall 149. The pocket 144 further may be described as having a height, which describes the radial height of the pocket 144. The pocket 144 further may be described as having a width, which describes the axial width of the pocket 144. In certain preferred embodiments, the size of the pocket 144 (i.e., the depth, height, and width of the pocket 144) may be described by how each relates the corresponding dimension of the platform 110 (i.e., the circumferential depth, radial height, and axial width of the platform 110, respectively). For example, in certain preferred embodiments, the depth of the pocket 144 may be between 0.1 and 0.6 times the circumferential depth of the platform 110. The height of the pocket 144 may be between 0.1 and 0.9 times the radial height of the platform 110. And, the width of the pocket 144 may be between 0.1 and 0.4 times the axial width of the platform 110. In certain other preferred embodiments, the depth of the pocket 144 may be between 0.2 and 0.3 times the circumferential depth of the platform 110. The height of the pocket 144 may be between 0.4 and 0.8 times the radial height of the platform 110. And, the width of the pocket 144 may be between 0.2 and 0.3 times the axial width of the platform 110.

As stated, the port 146 may have a significantly smaller cross-sectional flow area than cross-sectional flow area through the pocket 144 and the mouth 148. In certain preferred embodiments, the port 146 has a cross-sectional flow area that is between 0.1 and 0.6 times a cross-sectional flow area of the mouth 148. In certain other preferred embodiments, the port 146 has a cross-sectional flow area that is between 0.2 and 0.4 times a cross-sectional flow area of the mouth 148. It will be appreciated that this type of increase in cross-sectional flow area will slow the flow of coolant as it moves from the port 146 to the mouth 148 of the pocket 144.

The pocket 144, as stated, may include a port 146 formed in the inner wall 149. The port 149, via the cooling channel 136, fluidly links the pocket 144 to a supply of coolant. In a preferred embodiment, the port 146, via the cooling channel 136, connects to the plenum 132. It will be appreciated that the present invention may function with different types of coolant sources. For example, the port 146 could be connected to a channel that derives coolant from a shank cavity source, as discussed below in relation to FIG. 10. As illustrated, the port 146 may be disposed on the inner wall 149 of the pocket 144. The mouth 148, it will be appreciated, has a greater cross-sectional flow area than the port 146/cooling channel 136 that supply the pocket 144 with coolant. Another manner by which the pocket 144 may be described is that the pocket 144 includes a configuration that abruptly increases the cross-sectional flow area of the cooling channel 136 just before the cooling channel 136 reaches one of the slashfaces 122, 126.

In some embodiments, as illustrated in FIG. 10, neighboring pockets 144 may be connected via a pocket-to-pocket channel 151. The pocket-to-pocket channel 151 is configured to allow fluid communication between pockets 144. The pocket-to-pocket channel 151 may direct coolant to areas of greater need. FIG. 10 further includes an embodiment in which the cooling channel 136 links the pocket 144 to the shank cavity 119. In this case, a cooling channel 136 extends from the port 146 formed on the inner wall 149 of the pocket 144 to an underside port 155 positioned on the underside 114 of the platform 110. As illustrated, the pockets 144 may be axially concentrated along the pressure side slashface 126 between the leading edge 107 and the trailing edge 108 of the airfoil 102. In certain preferred embodiments, there may be between 4 and 8 pockets formed along the pressure side slashface 126. Additionally, in the same manner as described above, pockets 144 may be formed at a plenum outlet 133.

In some embodiments, as illustrated in FIG. 11, pockets 144 may include a discharge channel that connects the pocket 144 to the topside 113 of the platform 110, which will be referred to herein as a pocket-to-topside channel 161. Specifically, the pocket-to-topside channel 161 is configured to allow fluid communication between a port located on a ceiling or outboard inner surface of the pocket 144 and a topside sport 163 formed on the topside 113 of the platform 110. It will be appreciated that the pocket-to-topside channel 161 may allow a portion of the coolant flowing through the pocket 144 to be diverted to the topside 113 of the platform 110 for film cooling purposes. Though the pocket-to-topside channel 161 may be aligned otherwise, in a preferred embodiment, the pocket-to-topside channel 161 may be canted in the downstream direction, as illustrated. It will be appreciated that this directional alignment reduces coolant in a manner that reduces mixing losses as well as promoting greater film cooling efficiency.

In regard to the plenum 132, embodiments of the present invention may include a single or multiple plenums 132, as illustrated in FIG. 7. Each plenum 132 may be formed just inboard of the planar topside 113. As shown, in certain preferred embodiments, the plurality of plenums 132 may be provided within the pressure side of the platform 110. It will be appreciated that the features described herein also may be located on the suction side of the platform 110 and function similarly. In such a case, the pockets 144 will be disposed along the suction side slashface 122. An example of this type of embodiment is illustrated in FIG. 12. In one preferred embodiment, there may be a plenum 132 located in a forward area of the blade 100 and another located in the rearward area of the blade 100.

As provided in FIG. 7, one of the formed plenums 132 may be disposed in more of a forward position than the other. In a preferred embodiment, the plenum or plenums 132 may be aligned approximately parallel to the aft edge 121 and forward edge 124 of the platform 110, and may be configured as long and relatively narrow and hollow passageways. The plenum or plenums 132 may have a longitudinal axis that is parallel to the planar topside 126 of the platform 110. In certain embodiments, each of the plenums 132 extends from an interior position to a position on the pressure side slashface 126. In general, the plenums 132 may be configured to form a supply chamber from which smaller interior coolant passageways (i.e., the cooling channels 136) branch. A plurality of the cooling channels 136 may branch from each plenum 132. The cooling channels 136 may be linear and configured to extend away from the plenum 132. The cooling channels 136 may include a pocket 144 formed on one of the slashfaces. It will be appreciated that this arrangement may be used to effectively distribute coolant within the various regions of the platform 110, as discussed in more detail below.

In certain embodiments, a plenum 132 extends toward one of the slashfaces and, near the slashface, includes a plenum outlet 133 that connects to another pocket 144 formed at the pressure side slashface 126, as shown in FIG. 7, or the suction side slashface, as shown in FIG. 12. In the preferred embodiment of FIG. 7, the rearward plenum 132 includes a plenum outlet or outlet 133 at an aft position on the pressure side slashface 126, and the forward plenum 132 also may include a plenum outlet 133 at a forward position on the pressure side slashface 126. As illustrated, the plenum outlet 133 may be configured such that it has a cross-sectional flow area that is less than the cross-sectional flow area of the plenum 132. The cross-sectional flow area of the plenum outlets 133 may be reduced in this manner because of the need to evenly distribute coolant throughout the interior of the platform 110. That is, the plenum 132 may be designed to distribute coolant to the several cooling channels 136 with little pressure loss. To accomplish this, the cross-sectional flow area of the plenum 132 typically is significantly larger than the cross-sectional flow area of the cooling channels 136. It will be appreciated that if the plenum outlets 133 were not reduced in size compared to the size of the plenum 132, an inordinate amount of coolant would exit the platform 110 through the plenum outlet 133 and the supply of coolant available to the cooling channels 136 would be likely insufficient. The plenum outlets 133, thus, may be sized to have a cross-sectional flow area that corresponds to a desired metering characteristic. A “desired metering characteristic,” as used herein, refers to a flow area through the coolant passageway that corresponds or results in a desired distribution of coolant or expected distribution of coolant through the several coolant passageways and/or the outlets that are formed along the pressure side slashface 126.

In some embodiments, a plug 138 may be used to reduce the cross-sectional flow area of the plenum 132 such that the plenum outlet 133 is formed, as illustrated. The plug 138 may be formed such that, upon installation, it reduces the cross-sectional flow area through the cooling passage in which it resides. In this case, the plug 138 is configured to allow a desired level of coolant flow through the plenum outlet 133, with the remainder forced through alternative outlets. Specifically, the plug 138 may be configured to be inserted into the plenum 132 and reduce its cross-sectional flow area by blocking a portion of the flow area therethrough, thereby forming the plenum outlet 133. The plug 138 may be designed so that it reduces the flow area to a desired or predetermined cross-sectional flow area that relates to metering the coolant through the cooling configuration. In certain embodiments, as shown, the plug 138 may be formed with a central channel such that it forms an approximate “doughnut” shape. The plug 138 may be made of conventional materials and installed using conventional methods (i.e., welding, brazing, etc.). Once installed, an outer face of the plug 138 may reside flush in relation to the inner wall 149 of the pocket 144.

The connector 134, as shown, may extend in an approximate circumferential direction between the plenum 132 and the interior cooling passage 116. It will be appreciated that the connector 134 provides a passageway for an amount of coolant to flow from the interior cooling passage 116 to the plenum 132. In one embodiment, the connector 134 may be approximately parallel to the forward edge 124 and the aft edge 121 of the platform 110.

As stated, the cooling channels 136 may be configured such that each extends from the pressure side slashface 126 to a connection with the plenum 132. As shown, the cooling channels 136 may be linear. The longitudinal axis of the cooling channels 136 may be canted with respect to the longitudinal axis of the plenum 132. The cooling channels 136 have smaller cross-sectional flow areas than the plenum 132 and/or the connector 134. It will be appreciated that the cooling channels 136 may be configured such that, during operation, each cooling channel 136 flows coolant through a pocket 144 formed on the slashface.

As mentioned above, the pockets 144 and the related interior coolant passageways (i.e., the connector 134, the plenum 132, and the cooling channels 136) may be located on the suction side of the platform 110. As shown in FIG. 12, in such a case, the pockets 144 will be disposed along the suction side slashface 122.

In operation, it will be appreciated that the plenum 132, the connector 134, and the cooling channels 136 may be configured to direct a supply of coolant from the interior cooling passage 116 to a plurality of pockets 144 formed along the pressure side slashface 126 or the suction side slashface 122. More particularly, the platform cooling arrangement of the present invention extracts a portion of the coolant from the interior cooling passage 116 or shank cavity 119, uses the coolant to remove heat from the platform 110, and then expels the coolant by way of the pocket 144 formed within the slashface. Released in this manner, the coolant cools the area of the platform 110 that surrounds the pocket 144 without creating the steep thermal gradients associated with conventional impinged release techniques. As stated, this region is typically difficult to cool and, given the mechanical loads of the area, is a location that receives high distress, particularly as engine firing temperatures are further increased. The present application describes a manner by which the cooling requirements may be satisfied, while also discouraging the formation of undesirable thermal gradients within the slashfaces of the platform. As those of ordinary skill in the art will appreciate, this will extend the life of a rotor blade by reducing low cycle fatigue in the platform region.

As one of ordinary skill in the art will appreciate, the many varying features and configurations described above in relation to the several exemplary embodiments may be further selectively applied to form the other possible embodiments of the present invention. For the sake of brevity and taking into account the abilities of one of ordinary skill in the art, all of the possible iterations is not provided or discussed in detail, though all combinations and possible embodiments embraced by the several claims below or otherwise are intended to be part of the instant application. In addition, from the above description of several exemplary embodiments of the invention, those skilled in the art will perceive improvements, changes, and modifications. Such improvements, changes, and modifications within the skill of the art are also intended to be covered by the appended claims. Further, it should be apparent that the foregoing relates only to the described embodiments of the present application and that numerous changes and modifications may be made herein without departing from the spirit and scope of the application as defined by the following claims and the equivalents thereof. 

We claim:
 1. A platform cooling arrangement in a turbine rotor blade having a platform at an interface between an airfoil and a root, wherein the platform comprises a pressure side slashface and a suction side slashface, the platform cooling arrangement comprising: a cooling channel formed within the interior of the platform, the cooling channel extending from a first end toward one of the pressure side slashface and the suction side slashface; wherein, at a second end, the cooling channel comprises a pocket, the pocket comprises an abrupt increase in cross-sectional flow area just before the cooling channel reaches the one of the pressure side slashface and the suction side slashface.
 2. The platform cooling arrangement according to claim 1, wherein the first end of the cooling channel connects to a port formed at an underside of the platform, the port configured to fluidly communicate with a shank cavity cooling source during operation.
 3. The platform cooling arrangement according to claim 3, wherein the first end of the cooling channel connects to a plenum formed within the interior of the platform, the plenum comprising a cross-sectional flow area greater than a cross-sectional flow area of the cooling channel.
 4. The platform cooling arrangement according to claim 3, wherein the rotor blade includes an interior cooling passage formed therein that extends from a connection with a coolant source at the root of the rotor blade to at least the approximate radial height of the platform; further comprising a connector that connects the plenum to the interior cooling passage.
 5. The platform cooling arrangement according to claim 3, further comprising a plurality of cooling channels; wherein each of the plurality of cooling channels connects to the plenum at the first end; and wherein, at the second end, each of the plurality of cooling channels includes the pocket, each of the pockets comprising an abrupt increase in cross-sectional flow area just before the cooling channel reaches the one of the pressure side slashface and the suction side slashface.
 6. The platform cooling arrangement according to claim 5, wherein the plurality of pockets are disposed along the suction side slashface.
 7. The platform cooling arrangement according to claim 5, wherein the plurality of pockets are disposed at regular intervals along the pressure side slashface; and wherein the plurality of pockets comprises between 4 and 8 pockets.
 8. The platform cooling arrangement according to claim 5, wherein the plurality of pockets are dispersed along the pressure side slashface; and wherein each of the plurality of pockets comprises a concave depression formed in the pressure side slashface.
 9. The platform cooling arrangement according to claim 8, wherein each of the plurality of pockets includes a mouth coplanar to the pressure side slashface; wherein, from the mouth, each of the pockets extends into the platform a short distance and terminates at an inner wall, the inner wall residing opposite the mouth; wherein each of the pockets comprises a port through which coolant traveling through the cooling channel enters the pocket; and wherein the port is disposed on the inner wall of the pocket.
 10. The platform cooling arrangement according to claim 9, wherein the mouth of each of the plurality of pockets comprises a rectangular profile.
 11. The platform cooling arrangement according to claim 9, wherein each of the pockets comprises: a depth that defines a circumferential distance between the mouth and the inner wall; a height that defines a radial height of the pocket; a width that is an axial width of the pocket; wherein the pocket is configured such that the depth comprises 0.1 and 0.6 times a circumferential depth of the platform; wherein the height of the pocket is between 0.1 and 0.9 times a radial height of the platform; wherein the width of the pocket is between 0.1 and 0.4 times an axial width of the platform; and wherein the port comprises a cross-sectional flow area that is between 0.1 and 0.6 times a cross-sectional flow area of the mouth.
 12. The platform cooling arrangement according to claim 9, wherein each of the pockets comprises: a depth that defines a circumferential distance between the mouth and the inner wall; a height that defines a radial height of the pocket; a width that is an axial width of the pocket; wherein the pocket is configured such that the depth comprises 0.2 and 0.3 times a circumferential depth of the platform; wherein the height of the pocket is between 0.4 and 0.8 times a radial height of the platform; and wherein the width of the pocket is between 0.2 and 0.3 times an axial width of the platform; and wherein the port comprises a cross-sectional flow area that is between 0.2 and 0.4 times a cross-sectional flow area of the mouth.
 13. The platform cooling arrangement according to claim 8, wherein the mouth comprises a greater cross-sectional flow area than both the port and the cooling channel.
 14. The platform cooling arrangement according to claim 8, further comprising a pocket-to-pocket channel, the pocket-to-pocket channel comprising an interior channel that connects one of the plurality of pockets to a neighboring pocket.
 15. The platform cooling arrangement according to claim 14, wherein the pocket-to-pocket channel is parallel to the pressure side slashface and configured to allow fluid communication between the one pocket and the neighboring pocket.
 16. The platform cooling arrangement according to claim 14, wherein the pocket-to-pocket channel comprises a cross-sectional flow area that is less than the cross-sectional flow area of the mouth of each of the one pocket and the neighboring pocket.
 17. The platform cooling arrangement according to claim 8, further comprising a pocket-to-topside channel, the pocket-to-topside channel comprising an interior channel that connects one of the plurality of pockets to a topside of the platform.
 18. The platform cooling arrangement according to claim 17, wherein the pocket-to-topside channel is configured to allow fluid communication between a port located on an outboard inner surface of the pocket and a topside port formed on the topside of the platform.
 19. The platform cooling arrangement according to claim 17, wherein the pocket-to-topside channel comprises a cross-sectional flow area that is less than the cross-sectional flow area of the mouth of the pocket; and wherein the pocket-to-topside channel is canted in a downstream direction.
 20. The platform cooling arrangement according to claim 5, wherein the plenum comprises a hollow passageway, the plenum extending from an interior position to a position near one of the pressure side slashface and the suction side slashface; wherein the plenum includes an plenum outlet that connects to another pocket formed on the one of the pressure side slashface and the suction side slashface; and wherein the plenum outlet comprises a cross-sectional flow area that is less than the cross-sectional flow area of the plenum.
 21. The platform cooling arrangement according to claim 20, wherein the cross-sectional flow area of the plenum outlet is configured such that a desired metering characteristic is achieved.
 22. The platform cooling arrangement according to claim 21, further comprising a non-integral plug positioned between the plenum and the pocket, the non-integral plug configured to reduce the cross-sectional flow area of the plenum so to form the plenum outlet.
 23. The platform cooling arrangement according to claim 5, wherein the plenum comprises a supply chamber from which the plurality of cooling channels branch; and each of the plurality of cooling channels comprises a linear passageway that extends between the plenum and one of the pockets.
 24. The platform cooling arrangement according to claim 23, further comprising a plurality of plenums, each of which includes a plurality of cooling channels branching therefrom.
 25. A platform cooling arrangement in a turbine rotor blade having a platform at an interface between an airfoil and a root, wherein the rotor blade includes an interior cooling passage formed therein that extends from a connection with a coolant source at the root to at least the approximate radial height of the platform, wherein, along a side that coincides with a pressure side of the airfoil, a pressure side of the platform comprises a topside extending circumferentially from the airfoil to a pressure side slashface, and along a side that coincides with a suction side of the airfoil, a suction side of the platform comprises a topside extending circumferentially from the airfoil to a suction side slashface, the platform cooling arrangement comprising: a plenum residing just inboard of the planar topside and extending from an interior position to a position near one of the pressure side slashface and the suction side slashface of the platform, the plenum having a longitudinal axis that is approximately parallel to the planar topside; a connector that is configured to fluidly connect the plenum and the interior cooling passage; and a plurality of cooling channels, each of which includes, at a first end, a connection with the plenum and, at a second end, a pocket formed at the one of the pressure side slashface and the suction side slashface; wherein each of the pockets includes an abrupt increase in cross-sectional flow area of the cooling channel, the abrupt increase in cross-sectional flow area extending from a port formed along an inner wall of the pocket to a mouth coplanar to the one of the pressure side slashface and the suction side slashface over. 